Clutch Hydraulic system bleeding question.

I've re-read all the posts concerning this topic and I'm still confused. Hoping someone can enlighten me.

A few weeks ago, I replaced the clutch slave cylinder. Bled the system, had good pedal, drove it around a while with no problems. I DID notice that the clutch pedal engaged closer to the floor than before. So, I re-bled the system. Same result only that time, when the car sat a few minutes, the pedal went real soft. I could pump it up and get it into gear, but when downshifting, had to put it in neutral, pump a few times, then shift.

Yesterday, I re-bled again....same result. There are no leaks whatsover. The resevoir stays full after bleeding and topping off.

Some of the threads suggest injecting the fluid from the bottom up. This is what I don't understand. Wouldn't that just introduce air into the system? And, with the cap off on the master cylinder I'm thinking that I'd be pushing fluid up and out of the master and onto the floor and my shoes.

Sorry for the long version here, but I'm stumped.

Thanks,
Bill

I used the injection method...and then bled like normal. It helps to dislodge any pesky bubbles hiding in your slave cylinder.

If you are bleeding by yourself...just go up and suck some of the fluid out of your clutch MC after injecting a little...that will ensure you don't get fluid all over your pedal platform.

After going from the bottom up, I then reversed the process and bled from top down...but probably didn't need to. Just being a bit anal.

I found a simple hypodermic type plastic injector at a home supply store...it was a "flavor injector" kit for a few dollars. I added a short piece of hose to the end that fit the bleed nipple...sucked in fluid, then held it upside down and squirted till no air in the tube...then injected into the slave.

Some folks have gotten their injectors from veterinary pals...you can get some big ones there.

Hope that helps a bit!

Oh yeah...there is also lots of posts about the "proper" location of the bleed nipple on your slave. Do a quick search for lots of fun reading.

Tony

When doing the push bleed method I have found this to help;
Remove the slave from the trans, 2 bolts and 1 pin. (check for elongated holes)
Push the piston of the slave in and hold it there w/plastic cable tie or similar.
Orient the slave so the flex hose is at the top.
Inject fluid into the bleed nipple slowly making sure you dont overfill.
Its best to have the system full and suck out fluid from the master prior to bleeding as mentioned before. This way you wont overfill.
RS

Clamp the piston/push rod so it can not extend.
Bleed.
Release and bleed again.
Seems to solve the problem for me.

Before you go to all that trouble check to see if you have fluid behind the rubber boot of the master, and or on the back side of you clutch pedal. If so you need to replace the master. Then again you may have an internal leak in the master cylinder causing your problem.

As Tom said! All that pumping of an old master and pushing the seals into unknown territory can cause the seals to leak even though they were ok before.
Caution to anyone bleeding a known good MC - dont pump the pedal all the way down!
RS

I'm not losing any fluid at all. Would the leak you folks mention be sucking in air and causing the problem?

apologies in advance for being dim on this topic!

smirkinwill Wrote:

There are two seals in the master cylinder. If the inner one is leaking there want be any lost of fluid. Just the pressure will leak by the seal with in the master cylinder.

Main problem I had was I wasn't pushing the piston all the way back in. It goes in part of the way, and then kind of stops, but it is just hitting a spring, so there is still another little bit of travel to go. When I pushed it all the way in with the bleeder plug opened, I had a nice big air pocket shoot out at the very end. After that, hold it contracted, close the bleeder plug, then let go. Make sure the reservoir is full before doing this or you may suck in air, but also make sure you don't send it spewing because you push the piston in faster than the fluid can flow out of the bleeder plug...

Hurst

Thanks guys!

I'm going to have it checked out Wednesday at Carriage Craft in Reading, PA. I don't have the equipment (EZ Bleeder) nor, I fear the talent to correct this. Just wasting fluid is all I'm doing.

I do have a new clutch master cylinder in the box so if it turns out I wrecked the seals (as Tom suggests may be the issue) I'll have that replaced as well. (I have the new hose & washers too....just not on the car yet.)

Lesson learned from this is: When working on hydraulics, replace everything at once or it'll bleed you dry. Pun intended.

Putting the issue of leaks aside, I found that when I was bleeding mine using the two person system, it helped if the "pusher" snapped the pedal down very quickly each time. Using the gentle approach just didn't get all the air out of the system. Fozzie

You can also get a very nice syringe of good size at many Cooking shops.

one thing to be careful of....do not try to push the stuff in really fast...you'll blow the hose off the syringe and make a mess. steady pressure works.

Fozzie Bear Wrote:

I just bleed the clutch by removing the slave cylinder from the transmission and let it hang by the hose. Hose is attached at the end so that makes it the high point while hanging. Then I push the slave in a little ways by its pushrod, which forces the air at the top of the cylinder out into the hydraulic line. The bubbles rise and when I release the pushrod the internal spring pushes it back down which sucks more fluid in. By repeating this you eventually hear the air bubbles reach the master cylinder and it makes a gurgling sound. Just keep repeating this, pushing the slave in then letting it come back out, until the gurgling stops in the MC. No need to open the bleeders up even.

p.s. only do this with a new, newly rebuilt, or known clean slave cylinder that has no crud or corrosion inside. Otherwise, you could damage the seal or cylinder wall by pushing it in past its normal range of travel and into the cruddy area.

Yep, I didn;t really read thru all of the posts here, but, what Tom says, is what I was going to say.

If you have bled over and over and you have the bleeder in the PROPER HOLE, and you are loosing pedal, but not any fluid leak, then you have a bad master.

It can be rebuilt with ease. Just order the new rubber pieces and rebuild the clutch master!

Are you sure there is no leak at the slave, or up by the cmc itself?

If no leaks, and the bleeders in the right hole, it only leaves the cmc. and to tell you the truth, the fact that it pumps up, and then loses pressure is really screaming out bad rubber seal in the cmc.

GOOD LUCK,

B

Here is what I wrote several years ago;

After reading tech tips for winter “98 Moss Motoring, the article about bleeding clutch hydraulic systems. I thought I would give you a technique that has worked well for me.
Having owned a British car for 35+ years and working as a mechanic for 28+ years most of which was on imports. This is my “ one man “ technique. Take a “dedicated” pump oiler, empty and clean it, use a brake clean chemical to remove any residue of previous oils. Fill it with brake fluid of your choice, and pump until nothing but clean fluid comes out. Place a shop towel over the master cylinder to catch spills. It may be best to leave the fluid low until the procedure is done. Find a clean vacuum sized hose and slide it over the tip of the oiler. And the other end unto the “loosened bleeder screw of the slave cylinder. Keep an open end wrench handy to tighten the bleeder and pump fluid backwards. Pump at least 10- 12 times and tighten the bleeder screw. Wipe off the master cylinder and try the clutch. If it’s still muushy, try 10-12 times more.

Although I’ve given this procedure, it’s not my original idea. Credit goes to service manager from Velie Imports 1972. This has worked well for me on everything from my ’59 bug eye, my MGB, countless Mercedes, Datsun’s, and even on domestic cars I’ve had the misfortune to own or to work on. Motor on!
Dwight McCullough Ham Lake Minnesota

For what it's worth, any more if i have a car come into my shop with a leaking slave cylinder. Unless they have been replaced with in the last 5 or so years. I replace the intire clutch hydrolics system, master, hose,slave, push rod, and clevis pins. I do this for two reasons. I have found when the slave goes out the master isn't far behind. Also once you replace the slave and stop the major leak the pressure goes up and if the master has a weak spot it will come to light. It's kind of like a garden hose. If there is a small leak. I will only leak when the sprayer is shut off. Also I don't want my customer calling me in a couple of months because his clutch went away again because the master started leaking. Once I have replaced everything he should be good for 20 or more years. If he's like most of us he want have to deal with any clutch hydrolics problem in his life time.

Good advice Tom and I will do just that. Makes sense that after 40 years, if one really similar component of the system fails, the other components are just waiting to strike.

Luckily, I do have a new Lockheed master that I'll bring with me tomorrow along with a new hose and all the washers.

Thanks again all. Great forum!